Block Outgoing Program in GUFW

Hi Guys. I'm relativelly new to the Linux community. This is my first question ever about an issue I was not able to resolve on my own.

I want to permanently block a program running on by Debian SolydX distro from checking the web for updates. I have GUFW 12.10.0.

Now, I tried blocking using the pathway Add > Preconfigured > Deny > Out > Apploication ... but its not listed in the list of popular software which is actuallyu dominated byu P2P software. Then I tried the pathway Add > Simple > Deny > Out ... but cound not find a way to check which port the software uses.

How to check the port? Or, how to add my program to the Preconfigured list of programs?

If it's easier, I'll attack the problem via Terminal as per your advice.